The overall goal of the proposed project is to gain a better understanding of the neural mechanisms which regulate two forms of aggressive behavior elicited from the hypothalamus in the cat -- quiet biting (predatory) attack and affective defense behavior. In the past, a major thrust of this project was to identify how subthreshold electrical stimulation of the various components of the limbic forebrain modulated these two forms of aggressive behavior and to further describe the underlying neural pathways for modulation. Recently, we have begun to focus upon how seizure foci involving these limbic structures can modify hypothalamically-elicited aggression. Our initial studies, which are ongoing, involve the amygdala and pyriform cortex. The paradigm involves the elicitation of (acute) electrically- or (chronic) cobalt-induced seizures of sites in this region of the temporal lobe where prior subseizure electrical stimulation was capable of modulating one or both forms of the attack response and the assessment of the effects of these seizures upon aggressive reactions during the postictal period. Our strategy is to systematically describe how seizure foci of the various subnuclei within the amygdala, pyriform cortex and adjoining ventral hippocampal formation can modify attack thresholds. A related feature of this project is to identify the pathways utilized during focal seizure activity and their target structures in order to characterize the undelrying regions subserving epileptic modulation of aggression. These stuidies will be analyzed by the 14C 2-deoxyglucose (2DG) method in which 2DG will be administered during seizure activity and by electrophysiology in separate acute experiments. Other studies will examine: 1) how the midbrain periaqueductal gray (PAG) can modulate aggressive reactions and the possible role of the enkephalinergic system in such regulation, and 2) the distribution of fibers associated with aggressive reactions from the midbrain to both the forebrain and lower brainstem. Data to be derived from these studies will be fundamental to our understanding of several of the basic substrates and mechanisms which regulate aggressive behavior from the limbic-midbrain.